Combustion chamber foe a coal stove



April 24, 1951 J R FELLOWS 2,549,788

COMBUSTION 'CHA'MBER FOR A COAL STOVE AND AN AIR SUPPLY THERETO FiledMarch 21, 1945 3 Sheets-Sheet 1 l? as l I I 1 I April 24, 1951 J. R.FELLOWS 2,549,788

COMBUSTION CHAMBER FOR A com. STOVE AND AN AIR SUPPLY THERETO FiledMarch 21, 1945 3 Sheets-Sheet 2 y ziiw W VMW/ ' April 24, 1951 J. R.FELLOWS 2,549,788

COMBUSTION CHAMBER FOR A com. STOVE AND AN AIR SUPPLY THERETO 3Sheets-Sheet 5 Filed March 21, 1945 ei/azaz Fatented Apr. 24, 1951COMBUSTION cnaivienaroaaooni. s'r'ovE AND AN are SUPPLY THERETO JulianIt. Fellows, Urbana, Ill., assignor to The Board of Trustees of theUniversity of Illinois,

Urbana, Ill.

Application March 21, 1945 Serial No. 583,905

" 2 Claims. 1

This invention relates to a coal stove or the like for use in heatingresidences and other buildings.

All typesv of bituminous coal contain large amounts of combustiblevolatile matter which is not burned completely in the ordinary stove orfurnace. This not only wastes much of the fuel value of the coal, butalso results .in a dirty atmosphere. Various methods have been proposedfor burning the combustible vapors.

None of them are adaptable to simple stoves which could be purchased byfamilies whose in comes are in the lower income brackets.

I have invented a lightweight, inexpensive stove which uses thedown-draft principle of burning to consume the smoke. This new coalstove requires a minimum of attention, and is easily regulated so thatthe usable heat can be controlled. The new stove also provides for astorage space which can be filled with coal and will then require no.attention for considerable periods of time.

With the coal stove of this invention it is now possible to heat smallhomes with an efiicient consumption of fuel and at extremely low cost.This results in a substantial saving covering those portions of the yearin which heating is required.

The inventionwill be described as related to a typical embodiment of thesame set out in .n

accompanying drawings. Of the drawings, Fig. l is a cross-sectionalelevation taken along line l i of Fig. 2, of a coal stove embodying theprinciples of my invention; Fig. 2 is a plan view of the stove of Fig.i; Fig. 3 is a section taken along line 33 of Fig. i; Fig. 4 is asection taken along line 4-4 of Fig. 1; Fig. 5 is a section along line 5-5 of Fig. l; and, Fig. 6 is an elevation, partially broken away, of analternate embodiment of the invention. 7

The new coal stove illustrated in Figs. 1-5 of the accompanying drawingscomprises an outer Shell portion l0 holding a fire box it divided into aeokingzone l2, a coke-burning zone i3, and a combustion zone I l. At thebottom of the stove, and defining the fire box ii, there is located agrate l5. Beneath this grate is an ash receiving chamber [6 Which ismade accessible by means of an ash door H.- In the door il or at othersuitable location, there is located an air inlet opening l8 covered witha suitable draft regulator I9. At the top of the stove there is provideda feed opening 2%} that is kept normally closed by a dooi or lid 2%,here illustrated as a pm'g' type. It must fit reasonably tight.

Attached to the back of the stove, and in communication with thecombustion zone hi, there is located a curved radiator 22. This radiatoris designed to be heated by the products of combustion and to conveythis heat by radiation and convection to the room in which the stove islocated. The bottom 23 of the radiator serves as a trap for fly ash. Thefly ash may be removed in any suitable way at the side or rear. Asshown, the fly ash may be removed by opening the hinged door 24.

The stove has its combustion zone l4 located between the coke-burningzone I3 and the radi ator 22. The inner end of the combustion zone, orthat portion within the shell I0, is defined by the scoop 21 of ascoop-shaped refractory element 28 made of ceramic or suitable metalfastened in inverted position to the shell Ill of the stove by means ofa U-shaped bolt 2-9. The opposite end of the combustion chamber extendsinto the radiator, and this end is defined by an inverted box-likestructure as opened at the bottom. As can be seen from the abovedescrip= tion, the gases from the coke-burning zone It pass upwardlyinto the combustion zone 14 and then pass downwardly into the radiator22 before reaching the chimney through a smoke pipe 35, while the gasesfrom the coking zone come generally downwardly to join the gases fromthe coke burning chamber just before they enter the combustion zone. Inorder to provide a combustion surface in the combustion zone arefractory plate 32 is positioned at the top of the combustion zone. Inthe operation of the stove this refractory plate quickly becomes veryhot and provides an effective ignition surface. This is highlydesirable, but not essential to operation of the other features of theinvention.

'In order toprovide adequate supplies of air to the various zones, thereare located air supply channels within the stove. At the front of thestove there is positioned a primary air channel 33 extending from thespace adjacent the grates I5 to near the top of the fire box H. This :2channel has a number of small holes 34 communicating with the fire box.At the rear of the stove and beneath the combustion zone l-i there islocated a secondary air channel 35 ex tending. from the region adjacentthe grate to the entrance to the combustion zone. These two channels areprovided so thatthere can be an adequate supply of primary coking air,primary coke-burning air, and secondary air to the combustion zone. Thisair, as well as the air which flows through the grate, all entersthrough the opening 3. The secondary air channel is divided bylongitudinal partitions 3E into three small passageways 31 (Fig. 4). Inthe center one of these passageways there is located a small hole 38about in diameter, opening to the outside of the stove for providing aminimum supply of secondary air even when the draft regulator door [9 isclosed. Other means of introducing the secondary air may be substituted.

In the roof of the stove, which should otherwise be air-tight, there islocated a restricted openingBS about /2" in diameter. This hole ispositioned in that portion of the roof directly over the forward edge ofthe scoop. At the top of the stove there is provided a passageway ibextending from the top of the fire box H to the top of the radiator 22.This passageway is provided with a damper 4! which is normally kept inclosed position. This by-pass may be avoided by having a door suitablysmall.

In the operation of my new stove the fire box I I may be fired with coalthrough the feed opening 26. The coal at the top of the fire box in whatis referred to as the coking zone, is slowly converted to cokeprogressively upwards from the coke-burning zone i3. As the coke isburned the ashes may be removed through the grate l5, and the fresh cokeforced by its own weight into the coke-burning zone. The primary airchannel 33 which extends for the whole depth of the coal supplies air tothe coking zone and the cokeburning zone through holes 34 in thechannel. The number and size of these holes depends upon .ie size of thestove, and the heat requirements of the stove. In a typical example, thechannel is 6 wide and has three vertical lines of T g" holes 1 apart.This is adequate for a stove with a fire box approximately 19" indiameter and 24 deep. The primary air channel 33 is preferably locatedat the front of the stove opposite the combustion zone and just abovethe air inlet opening. Air is supplied to the combustion zone by meansof a secondary channel located at the rear of the stove and incommunication with the combustion zone. In the structure shown airenters the inlet opening eneath the grates it. From here a portion ofthe air flows up through the primary air channel 33 for the full lengthof the coal, another portion through the secondary channel 35 to thecombustion Zone and the remainder through the grate to the bottom of thecoke-burning zone. Such a construction provides an adequate supply ofair for coking the coal, burning the coke, and consuming the gasesevolved in these two operations. When the air inlet opening 58 is closedby its door [9 adequate supplies of air are provided to the combustionzone through opening 38 to maintain a smokeless pilot fire.

The restricted opening 39 in the roof of the stove supplies air to thetop of the coking zone and prevents the accumulation of that criticalamount of gas causing the phenomenon known as puff back. A puff back iscaused by certain critical amounts of gas and air that accumulate andthen ignite with a slight explosion. Restricted opening as may bestrategically located in such a way that the air passing through itimpinges on the surface of the bed of fresh coal in a small area closeto the edge of the scoop 21. This air jet is very helpful in eliminatingpuff back because it localizes the coking process when the regulator I9is closed and it also tends to maintain a pilot flame in one spot on topof the coal bed which burns the gases which are re- IB into the regionleased during a hold fire period. The efiectiveness of this jet of airmay be increased by extending a tube downwardly from air opening 39 fora distance of approximately 4". The opening has an additional purpose inthat it prevents the coal in the coking chamber from arching over. Ithas been found that in most downdraft magazine stoves when the coal isconverted to coke it forms a solid mass extending from wall to wall.Portions at the bottom of the coke chamber will fall into thecoke-burning zone, but those at the top sometimes form. an arch andremain suspended above the coke-burning zone. This is particularly trueat low burning rates. The arching over does not occur in this stovebecause air entering restricted opening 39 causes the coke near the sideof the stove immediately beneath the opening to burn out, therebybreaking the arch. It has been found that when the air supplies havebeen shut off in the stove, as when it is only desired to maintain fireand not supply appreciable quantities of heat, when the stove is againput into active operation all the coke beneath the opening 39 has beenconsumed and the rest of the coke feeds by gravity down into thecoke-burning zone. The openings 34 from passage 33 have the same eifectduring normal operation.

The passageway 4d at the top of the stove is provided so that smoke willnot escape from the feed opening 2e when the feed door 2| is removed.The operation is as follows: Before the feed door II is opened thedamper 4! is turned to open position. This permits all the smoke in thetop of the fire box to escape out the passageway 40 into the smoke pipe31.

The combustion of the gases evolved in operation of the stove takesplace in the combustion zone M. These gases leave the coking zone 12 andcoke-burning zone 53, pass into the combustion zone, and are then mixedwith secondary air and ignited beneath the refractory element 32.

The fire box it should be lined with a refractory material 22 such asheat-resisting brick. It could be constructed however from a suitablemetal.

An alternate embodiment of this stove is shown in Fig. 6. Thisembodiment has no radiator, and the combustion zone Ma extends from thetop of the coke-burning zone 13a to the top of the fire box. Thiscombustion zone is vertical and is connected directly to smoke pipe 31a.The combustion zone is separated from the rest of the fire box by avertical refractory element 43. The embodiment of the invention shown inFig. 6 is provided with a primary air channel 58 similar to the channel33 (Figs. 1 and 3) and a restricted opening 5! similar to the opening 39(Fig. l). This alternate form of stove is still cheaper to constructthan the first form, and also provides for the emcient consumption ofcoal.

Tests made on this new stove show that the coal is burned with very highefficiency. The carbon dioxide in the flue gases has been found to beremarkably high under all conditions.

Having described my invention in considerable detail, it is my intentionthat the invention be not limited by these details but rather beconstrued broadly within its spirit and scope as set out in theaccompanying claims.

I claim:

1. A coal stove and the like comprising a fire box having therein acoking zone and a cokeburning zone, a combustion chamber incornmunication with but separate from said zones,

said combustion chamber extending partially inside and partially outsideof the fire box, a grate beneath the fire box, a roof above the firebox, a flue communicating with the combustion chamber, means forsupplying air to said zones and said combustion chamber, and ascoop-shaped refractory element fastened in inverted posi tion to theinner side of the stove ,with the scoop portion of said element definingthe fire box end of the combustion chamber, said scoop portion havingthe hollow part thereof toward the center of the combustion chamber.

2. A coal stove or the like comprising a fire box having therein acoking zone and a cokeburning zone, a combustion chamber at one side ofthe stove communicating with but separate from said two zones, a gratebelow the fire box, a roof above the fire box with a feed openingtherein having a tightly fitting door, a fine communicating with thecombustion zone, an air inlet below the grate, a perpendicular channelextending substantially the entire length of the fire box communicatingwith the air supply and having spaced perforations communicating withthe coking and coke-burning zones of'the fire box, a secondperpendicular channel located adjacent to but separated from thecoke-burning zone and extending to the combustion chamber from thebottom of the stove, said second channel communicating with the airsupply from said air inlet for providing secondary air to the combustionchamber, said second perpendicular channel being divided intolongitudinal subchannels by partitions with at least one subchannelhaving a small bleed h01e communicating with the outside of the stove,and at least one sub-channel being solid without such a bleed hole.

JULIAN R. FELLOWS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 91,857 Mayhew June 29, 1869228,061 Gregory May 25, 1880 231,163 Hamlin Aug. 17, 1880 242,126 HareMay 31, 1881 396,905 Wells Jan. 29, 1889 1,561,497 Wier Nov. 17, 19252,295,781 Fellows et al. Sept. 15, 1942' 2,330,094 Van Hoose Sept. 21,1943 FOREIGN PATENTS Number Country Date 52,313 Denmark Oct. 19, 1936575,138 Germany Apr. 28, 1933 774,722 France June 18, 1934

